EI will never fly with an empty seat in J if they can avoid it.
Revenue will release every seat possible for upgrade if they can't sell them, so once they have cleared the bid to upgrade (and they will decline low ball offers) whats left is release. if the flight is lightly booked the odds are you will get the upgrade in time. The actual 'allocation' is 2 seats on a A330, 1 on a A321?